How much did you pay? It sounds like a scam site. Pro costs $18.88 USD for 6 months of updates & email support. LW basic is free. There's no lifetime membership for Pro.
It's up to you whether you want to keep what you've got. I'd advise you to contact your bank/CC company & report this, they may be able to cancel the transaction for you. Then try out LW basic, or buy Pro from the official site where you'll get a clean version. The only official site for downloading either version is www.limewire.com

Check out the 2 threads below
http://www.gnutellaforums.com/showthread.php?t=28751

http://www.gnutellaforums.com/showthread.php?t=44499